On May 12, a message appeared in a new WhatsApp channel, called "Death to the Arabs". The message urged Israelis to join a mass street brawl against Palestinian citizens of Israel.

Within hours, dozens of other new WhatsApp groups popped up with variations of the same name and message. The groups soon organised a 6pm start time for a clash in Bat Yam, a town on Israel's coast.

"Together we organise and together we act," read a message in one of the WhatsApp groups. "Tell your friends to join the group, because here we know how to defend Jewish honour."

That evening, live scenes aired of black-clad Israelis smashing car windows and roaming the streets of Bat Yam. The mob pulled one man they presumed to be Arab from his car and beat him unconscious. He was hospitalised in serious condition.

The episode was one of dozens across Israel that the authorities have linked to a surge of activity by Jewish extremists on WhatsApp, the encrypted messaging service owned by Facebook.

The WhatsApp groups, with names like "The Jewish Guard", have added hundreds of new members a day over the past week, according to The Times' analysis. The groups, which are in Hebrew, have also been featured on e-mail lists and online message boards used by far-right extremists in Israel.

While social media and messaging apps have been used in the past to spread hate speech and inspire violence, these WhatsApp groups go further, researchers said. That is because the groups are explicitly planning and executing violent acts against Palestinian citizens of Israel, who make up roughly 20 per cent of the population and live largely integrated lives with Jewish neighbours. 안전카지노사이트